1. Field of the Invention
This invention relates generally to a method for attaching a stud pin to a cathode ray tube panel and more particularly, is directed to improvements of the frit slurry used for attaching the stud pin to the cathode ray tube panel.
2. Description of the Prior Art
In a cathode ray tube of a color television receiver, as shown in FIG. 1, a color selecting electrode 1 such as an aperture grille, a shadow mask and so on is attached through a leaf spring 2 provided on the color selecting electrode 1 to a cathode ray tube panel 3. More specifically, an aperture (not shown) formed through the leaf spring 2 is engaged with a stud pin 4 with a frustconical shape made of metal or ceramics and attached to the inner surface of the cathode ray tube panel 3 to thereby support the color selecting electrode 1 at a predetermined position. The color selecting electrode 1 shown in FIG. 1 is the aperture grille. In this case, the stud pin 4 is attached to the inner surface of the cathode ray tube panel 3 by using a frit slurry as a bonding agent.
As a prior art method for attaching the stud pin 4 to the cathode ray tube panel 3 by using the frit slurry, there has been proposed such a method as disclosed in the published document of, for example, Japanese patent application examined No. 33651/1983, in which the stud pin 4 having deposited thereon a glassy state solder glass or frit slurry 5 is accurately positioned relative to the inner surface of the cathode ray tube panel 3 by using a jig and then it is fixed to the cathode ray tube panel 3 by a clip (setting jig), it is subjected to the heating treatment to crystalize the frit slurry 5, thus the stud pin 4 being fixed to the cathode ray tube panel 3 at its predetermined position. In the case of this attaching method, considering the amount of the frit slurry 5 protruded around the stud pin 4, it is necessary to select the thickness of the frit slurry 5 before being subject to the heating treatment to be more than 10 times the thickness after being fixed. Since the frit slurry 5 is so thick as set forth just above, there is a problem that as shown in FIG. 2, during the heating treatment for recrystalizing the frit slurry 5, the stud pin 4 is sunk and moved by the elastic force of the clip or jig whereby after the stud pin 4 is fixed to the cathode ray tube panel 3, the positioning accuracy of the stud pin 4 provided before the heating treatment can not be maintained. This problem becomes serious particularly when producing a cathode ray tube of high definition.
As a method of attaching the stud pin 4 to the cathode ray tube panel 3 which can solve the above-mentioned problem, there has been proposed a method as disclosed in the published document of Japanese patent application examined No. 9020/1979, in which before the solvent contained in the frit slurry 5 is evaporated, the stud pin 4 is positioned relative to the panel 3 and then ultrasonic waves and so on are applied to the frit slurry 5 to thereby attach the stud pin 4 to the panel 3. Generally, as the frit material, a special crystalizing solder glass having a low melting point and whose specific gravity is as heavy as 6.1, for example, Pyroceram cement (product name) is used. Since this crystalizing solder glass contains lead oxide with a mixed amount of about 75% in total amount, it is not possible to use a binder and a solvent which will make a reducing atmosphere when they are heated and baked. For this reason, as the solvent therefor, there is used, for example, isopropyl alcohol (boiling point is 82.4.degree. C.) of quick drying property. As a result, the attaching work must be carried out skillfully and hence the workability thereof becomes poor, resulting from problems in a mass-productivity and automation standpoint.